A substrate stage is used in a plasma treatment apparatus for various substrates (hereinafter also referred to generically as substrate simply) such as a glass substrate for FPD, a semiconductor wafer, etc. In the background art, for example, an electrostatic chuck for attracting a wafer by use of an electric Coulomb force is used as the substrate stage. In addition, as for the structure of the electrostatic chuck, a mono-pole type and a bi-pole type are used. In the mono-pole type, a potential difference is provided between an electrode inside the electrostatic chuck and a substrate so as to attract the substrate. In the bi-pole type, an electrode is divided into two or more pieces inside the electrostatic chuck, and a positive or negative potential to the ground is applied to each piece so as to attract a substrate.
Particularly in some kind of electrostatic chuck for a glass substrate, a pair of semicircular, ring-like or concentric plane electrodes are used and an electric potential difference is applied between the plane electrodes so as to electrostatically attract the substrate. This electrostatic chuck is constituted by an inner electrode, an insulating film and a ring-like outer electrode outside the inner electrode, and further an insulating film (dielectric film) for electrostatic attraction.
Inside the inner electrode, a coolant channel is formed while a ring-like concave portion is, for example, formed to form the outer electrode in the upper surface.
In addition, the inner electrode is produced out of a conductive material such as an aluminum alloy or the like, and an insulating material coating this conductive material and a ring electrode. That is, the outer electrode formed out of a conductive material such as tungsten or the like is provided like a ring on the concave portion of the upper surface of the inner electrode through an insulating film formed out of a multi-layer thermally sprayed film (alumina in this case). This insulating film is located between the inner electrode and the ring-like outer electrode so as to secure electrostatic insulation between the two electrodes. Further, an insulating film composed of a thermally sprayed film (alumina in this case) may be formed on the surfaces of the inner electrode and the ring-like outer electrode (e.g. see JP-A-10-150100, pp. 5-6, paragraph [0021], and FIGS. 1 and 2), or a so-called comb-like electrode is used as an electrode shape (e.g. see JP-A-11-354504, pp. 9-10, paragraph [0049], and FIG. 1(c)).